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Monday, December 28, 2009

I have been planning to do more code practice and I want to buy a KX1 or similar transceiver. But I am very rusty, and for me, my code speed does not justify the investment. I would be embarrassed to put myself on the air. I try to listen to code while at my bench and workstation, and sometimes have received fun QSO's to try to copy - I am getting faster.

Yesterday I decided to do something about obtaining a MP3 player to contain code lessons as I think I would like to practice while away from the shop and radios, and maybe in the car. Thinking to myself that an investment of, . . say $150 for an MP3 player would be OK.

Boy, was I pleasantly surprised! (where have I been?)

At Staples, a more than adequate MP3 player (Coby) was only $29, and an even simpler players was only $19, both had 2G's of memory. I went for the $29 version because it had a built in USB connector, like a memory stick. Once pluged in, files are transfer as easy as file copy!

Now, all I need are some MP3 code files. Sometime ago, I found a WEB site that would generated CW MP3 downloadable files from typed text, I'll have looked but can not seem to re-find it.

Yesterday, Dave - W7AGJ came by my Shop. He had been to RPC (PC Recycling) in Seattle to buy a heat sink for a Home Brew Power Meter that he is building,

The large (about 6x5 inch) heat sink needed some of it's fins milled off of one side to provide a flat surface to mount to a the side of an enclosure he was planing to use. A lot of mill chips later, the heat sink was ready to mount. But, the aluminium enclosure was painted which prevents direct contact - after taping a mask (or shield) a paint patch, the size of the heat sink, was removed with the sand blaster.

Before leaving we discussed the frequency response of capacitors, Dave will need several for his voltage divider and detector circuit of the power meter. His goal is to provide reliable response from HF to 70cm (450mHz).

Using my AIM-4170B it was easy to see the effects of lead length and the different types of capacitors - it was not looking good for my best and available junk box capacitors above 150mHz. Dave is hoping to select the diode, capacitor type, lead length and construction methods to minimise the need for radical calibration chart - we will see. One idea, is to use several; Parallel, Surface Mount or Mica Capacitors.

Dave will no doubt want to scan his new project with an analyser with a greater frequency range than that which is possible with an AIM-4170B (1-181mHz).

I will continue to follow this project.

NOTE: RPC as mentioned above is a great place to find parts for Home Brew QRP project, re-purposed PC boards/equipment/parts are abundant for only very few dollars.

Saturday, December 26, 2009

I have measured the wire length or the inside of the conduit at 5.7m (18.70 feet) and calculated 1.81m (5.95 feet) Diameter (see previous post).

I re-scanned the antenna with the tuning Cap (4-47pF) at Maximum and again at Minimum. The both results are shown on the following graph.

Scan with Tuning Cap at Max and Min

Scale: 2 to 18mHz

The tuning Cap can vary the Resonant Frequency between 7 and 16mHz, just right for a 30m loop. This is very close to resonate frequencies as computed via a online calculator by Bruce Carter Loop Antenna Page.

All of the above was found experimental, now I an trying to justify it with math.

I know the impedance as seen at the feed point can be set by changing the turns ratios of the input toroid, The input impedance value is not critical for just looking at resonates, but it will be corrected before obtaining the final results. Currently the match is:

75 ohm input * (2 T Sec / 4 T Pri )^2 = 18.75 ohms output

According to what I have read on the Internet, the input impedance for a loop antenna is closer to 5 ohms. I should need a high turns ratio, like:

75 ohm input * (2 T Sec / 8 T Pri )^2 = 4.65 ohms output

With the tuning cap set to minimum, I would think the antenna would look like a dipole and resonate at:

22.88mHz = ( 300m / (5.7m * 2 * 1.15)

But, I measured 16.43mHz, maybe this is because the ends of the dipole are folded back in a circle and provide capacitance between the ends. Also, there is probably more self inductance due to the coil shape?

Note: I know that using a 12 AWG wire for the element is not the best for performance, but for design investigation it works just fine. Later it maybe replaced with stand alone copper pipe.

Thursday, December 24, 2009

Not knowing exactly what I was doing I started with Grey PVC Conduit and Electrical Box Fittings. I used two 10 foot sections bent into a circle with a square box fitting at the bottom and a tee pull-box at the top. The loop is about 19 feet in circumference (a little was cut off to remove the bell ends). Bending was done last summer in the hot sun. I have made two of these and have done different experiments on each - and, have learned something new at each revision.

Top of the loop Tuning 4-47pF Cap

The Bottom Box, with Toroid Core for Matching

(sorry, my old camera can not take a good photo for here)

Somewhere I had read that a single loop antenna had a very low impedance feed point 180 deg from the top or from the tuning capacitor. I used 12 AWG as the element inside of the conduit, looping through the conduit from the top, down to the toroid and back up to the top (that was fun!?).

Loop Schematic
(Now measured at 18.70 feet Circumference)

30m Loop As-Built

Experientially, I found a 4x2 turn toroid would provide a close match to my 75 ohm feed source, I used my AIM-4170B to check the feed performance. Also, during the experiment I found that 4-47pF cap would resonate the loop at 30m (10.140mHz). With a little tweaking of the toroid turn count and ratio, I should be able to get a low 1:1 SWR.

When I did all of this, I only had QRSS station and Grabber running, I did not have WSPR to make proper antenna comparison measurement. But. it did work well for both QRP QRSS Transmit and Grabber operation.

Recently, I have been reading Joachim's blog, where he describes the DCTL (Distributed Capacitance Twisted Loop) antenna. Well, my antenna looks somewhat like a DCTL antenna, only it has a lump capacitor at the top. I have started thinking I should rewire it with 300 ohm twin lead and driving it with my toroid transformer.

The next experiment, is going to use 300 ohm Twin Lead for the element. My concern is not the actual resonate frequency, only it's feed point behaviour, I can fix the resonate frequency later by change the loop size or a tuning cap.

My goal is to build a loop that is simple and easy, and that will be easy to keep in tune.

UPDATE1:

I have measured the wire length or the inside of the conduit at 5.7m (18.70 feet) and calculated 1.81m (5.95 feet) Diameter.

Yesterday, I learned of the death of a previous flying friend - Arden Johnson (of N2425Q), he pass away in March 2009. We had a "falling out" many years ago, and only spoke to each other a couple of times since. I wished that we had resolved our differences - but due to distance and other factors that did not allow two stubborn old-men to take the time to try.

In some way I thought we would resolve our differences someday, as I still have a metal file that he lent me. Each time I saw it in my tool cabinet, I remember I needed to return it - thinking that I could use it as an excuse to chat.

Looking back now, I can see that Arden may have tried, by asking us to their house to help resolve a new issues at the Airpark, we went to their house, but the Airpark was no longer important as we had just bought our new Ranch and was very busy with it. He left the door open for making amends, but due to other immediate Ranch issues, I just did not walk through.

It is strange how final death is, things un-said or un-done can not be corrected - no matter how hard you would want to try.

Brandon is a new HAM and has plans to build some VHS antennas and maybe a HS dipole. Because Brandon represents a younger adult, Tess (my dog) was in heaven, Brandon was someone to play ball with.

Dave - W7AGJ from SkyValley came by, he wanted more information on my Cordless Soldering Iron - he was looking for proper specification for describing it to Santa.

The Beacon Hunt

The hidden QRSS "Beac-in" was located by Jeff - KO7M within about 15 minutes of his arrival, using a portable Elecraft KX1 Transceiver with a clip lead from the antenna jack to his umbrella frame (it was raining). Jeff used low RF gain on the Transceiver and signal strength to Home in on the Beacon. Later, Jeff admitted that physcology was also used, as he looked in places that he thought I would have used for the hiding place. For the next hunt, I will try to make the hunt and physcology much harder.

For being the first to find the Beacon, Jeff will receive the prize - A pick of one of my QRSS/WSPR marker beacons, or a custom copy that we build during the event. He chose a custom copy - more on that later.

The Projects

Roger - K7RXV brought a very special KIT for all to enjoy, his kit was the fixings for Russian Mushroom and Potato Soup. He started just after arrival, he was busy chopping, cutting and saute'ing bits-n-pieces for what seemed like several hours, it was ready on-time for lunch. It was excellent, I highly recommend it! I plan to save the above link to the recipe for another time. Good job Roger!

Roger - Working at his Cook KIT

Jeff - KO7M brought his Elecraft KX1 Transceiver, we enjoyed listing to CW QSO's and his operations. We had to ask him to connect it up to some speakers for all to hear.

Jeff - Transceiver Operation

John - KC7NVE brought one of his KITs, A Scout Regen Receiver (I think) to start the build process, on arrival John had a sack of parts and boards. When he left, his parts were all labeled, organised and sequenced for easy access for the later build process. Not only is John a great HAM, he is an amazing organiser.

John - Labeling Parts for his KIT

Doug - W7RDP brought the chassis of a KIT he was starting, it needed holes drilled, punched, and the heat sink tapped. Doug spent most of his time at the Drill-Mill and helping with other projects.

Doug - Supporting Jeff's Marker Build Project

At the Mill/Drill

More Hardware Discussions in the Shop

Jeff - Hard at Work on a small SMD

Lunch

Thanks to: Carolyn (my sister) for helping with cookies and Tacos; and Roger for the Potato Soup. We had enough food for an army - I was stuffed.

Lunch Break

The Beacon Hunt Prize

For Jeff's Beacon Hunt prize, we went through the complete project, from a custom modified PCB layout on the computer screen, to a finished working Marker Beacon. We changed the layout to include his CALL on the artwork for the PCB. We used the Toner-Transfer Method to build the PCB. I installed the first part, Jeff installed all of the rest, using the schematic and a previous working beacon as a guide.

Marker, Still Under Construction

Jeff - Hard at Work under to Magnifier

On the first turn-on, only a chirp was heard on the receiver when the key was pressed. We inadvertently used an old junk battery that was sitting on the bench that was almost dead. The circuit board was double-sided taped to the battery and had to be removed. With a new battery, we tried it again - this time nothing! It did not make a sound at the receiver.

It is now trouble shooting time! Jeff compared the voltages between the working Beacon and his new Beacon, all voltages were the same. Because we used a new untried crystal in this Beacon, it was suspect - maybe it just would not oscillate. Remember this circuit is made of all surface mount components, and therefore it is somewhat difficult to check individual components. When a circuit has never worked before, it is sometimes difficult to know where to start troubleshooting.

We decided to remove the crystal and replace it with another. While cleaning the pads with solder wick to receive the second crystal, the series capacitor moved. That is, one half of the capacitor fell off, with the other end still soldered to the board. This was surely the problem - a cracked capacitor. We may have cracked the capacitor while prying the circuit off of the the old battery.

We replaced the capacitor, and did a trial press fit of the crystal in place - it worked! About this time, my Soldering Iron was low on battery charge, and therefore we had to wait for it to charge, to see the real results (don't ya just hate that?)

In the end, after the crystal was properly installed, a quick twist of the tuning trimmer put the Marker on frequency (10.140100mHz) . The Project was a success!

Other Topics

Sometime during the day we discussed a QRSS Beacon balloon launch (see previous post), many aspect of a balloon project are still up-in-the-air (no pun intended). To be successful, we will need to enlist as many US Grabber as available. From our Seattle area, the upper wind is just right for a long flight across the US.

Jeff also brought in his fantastic Valve (Tube) Regen Receiver. There has been a lot of talk about valve receivers on the WEB recently and I had forgot how enjoyable it is to look at the glow of a valve while in operation. From that dull red glow comes the magic that got me into HAM Radio in the first place, many years ago. It was good to hear and see Jeff's receiver.

The Dull Red Magic Glow of from Valve Receiver,

Unlike smoke, the Glow is something that you DO enjoy letting out of a Component.

(I think John may have a better photo, I'll see if I can get a replacement)

Update: Thanks to John the following four photos are added.

Now, . . . This is What The Magic Is All About!!

ReGen Receiver In Operation

Jeff - Working with his Regen Receiver

Conclusion

Because the winter evening come early in Seattle, the group left about 5pm - I enjoyed the day of having the guys at the Shop.

Tess enjoyed the attention and playing ball with all of the guys, she was dead tired by the end of the day. After going bed, I don't think she moved all night.

Wednesday, December 16, 2009

Last night I went to our monthly Puget Sound QRP (pQRP) P&C (pie and coffee) meeting.

For the event the group decided to do a White Elephant Gift Exchange, supposedly giving something from our junk box. I checked my junk boxes for an appropriate gift to take - it was something that I would have liked to have received, and wraped it for the exchange.

At the meeting and after dinner, I was one of the last to pick a gift from the gift pile, I selected a small package and was surprised. It was a Soft Rock 40 Kit (a receiver) - Very nice gift from someone that has an very impressive junk box. But, sad to say, in keeping with the rules of the White Elephant Gift Exchange, my Soft Rock Kit was taken by Alan K6ZY (the next in line to pick a gift), Dang! ;-(

OK, as per the rules, I had to pick another gift, again I picked a small gift and to my surprise, it was a TAK-40 Kit (a Transceiver, parts and boards). Again, some of the guys at the meeting must have very impressive junk boxes. Yet, not knowing exactly what a "TAK-40" was, after the meeting and at home, I spent several hours on the web reading and learning all that I could about it. Sometime early the next morning I got to sleep.

Well, I am thankful to who ever provided the Gift, I will put it to very good use, I may even spend some time increasing my code speed - Thanks.

UPDATE 1:

After reading much more on the web, The TAK-40 looks like it is going to be a bit of a project, to find; construction details, modification details, and all sorts of information to ingest and digest.

Let me know if you have a special demonstration that you would like to present, it can be scheduled so all will know.

Note: Due to the extremely cold weather and the heaved ground under the front concrete slab, the normal front door is ajar and will not open - use the large High Bay door.

For this event, I am looking for a volunteer to "Meet Greet", take names and take project photos, I missed doing so at the last event and was not able to include everyone in the follow-up report. Anyone interested?

Unlike most similar events, there will NOT be the usual "talk-in" frequency, but in keeping with my interest of Beacons, there is instead a QRSS "Beac-in" frequency to help guide your way at 10.140050mHz (+- a few). For a real map see the link below. Also, once you arrive, there is a prize for the first person to find the actual Beacon, hidden on the 40 acres. If found, don't reveal it's location, while others try. Bring your DF equipment and join in the fun.

The beacon was not found last month, so we well try again!

Due to the possibility of cold unpredictable weather, the outside "BBQ" will be replaced with indoor Tortillas and Fixings (or other snacks), bring additions to share if your like. For brave soles, the wood outdoor fire pit/BBQ is available if you tend the fire.

If wanted, as before I will re-demo PCB generation for new comers, Etch and SMD soldering. If you would like to try your hand at this, junk boards will be available.

Saturday, December 12, 2009

In 32 years living near Seattle, I have never seen it this cold! - For the last few weeks the night time temp has be around 10F with daytime temps about 20F. Normally we get two weeks of cool but nice clear weather in November, but now it is very clear and very cold. One night I measure 7F.

I have often told newcomers to Seattle, that we normally get 4 inches of snow (some years) and the mud puddles will freeze maybe once each winter - so far this is a very unusual year. Note: last year we got 29 inches snow, measured on my picnic table (the table in my photo with my dog Tess)

The ground has frozen and has heaved in large patches, my whole gravel drive way has heaved and now has ditches along the edges where none were before. We have had heaving before, with 2 inch sharp spears of ice crystals, pushing up through the surface, but this time the whole ground has heaved as one solid mass.

The covered porch/drive slab of concrete in front of my Shop had moved up enough that my shop man-door will not open. The slab is about 8 inches think in that area and I would have not thought that ice would have formed under it. The door is about 24 feet under the cover area.

In the main shop high bay area, I have the remains of my "ET Phone Home" QRSS Transmitter timer mechanism which is a 4 foot x 6 inch tube full of water which is now ice - now froze solid! pushing up it cover. It is located about 16 feet inside the shop.

The weather man says that it should start warming up soon, I sure hope so!

Thursday, December 3, 2009

Most of the day my receiver (R-2000) was tuned for WSPR on 500kHz, my lonely red flag shows up on the LF/ULF WSPR map near Seattle. There is only one transmitting station, N4QLB, in the US - I was hoping to a least log it. But no Joy.

Listening in Seattle, . . . . .

UPDATE:
I listened to 500kHz for two days - nothing but four bogus spots with bad CALLs and/or Grids - so, now Rx QSY to a higher band.

Wednesday, December 2, 2009

The last few days I have been very busy with tedious non-Ham Radio activitives, on this short break from that, I will dump what is in my head.

I put together an external Audio Isolation Transformer for my 30m Grabber Direct Conversion Receiver. This should remove the 60 and 120Hz hum-bars as displayed on the 30m Grabber. The transformer is not exactly a 600 Ohm Audio transformer, but it will work for now.

I also put in a Stereo Jack with the correct wiring so that I can now do away with the previously used adaptor. I made the mistake when building the receiver by not installing a stereo jack in the first place.

The temporary fix if ready, it works on my bench, now all have to do is find time to goto the receiver site and plug it in.

Also, I was reading Joachim's blog, where he describes the DCTL (Distributed Capacitance Twisted Loop) antenna - it is recommended reading. I like loop antennas!, with my new understanding of the DCTL, I may try it.